Vampire for one beginning to explode in rage (4)
I believe the answer is:
bate
'rage' is the definition.
(I've seen this before)
'vampire for one beginning to explode' is the wordplay.
'vampire' becomes 'bat' (I've seen this in another clue).
'for' says to put letters next to each other.
'one beginning to' says to take the initial letters.
The first letter of 'explode' is 'e'.
'bat'+'e'='BATE'
'in' is the link.
(Other definitions for bate that I've seen before include "decrease" , "Rage; beat the wings" , "contention for old poet" , "Lessen" .)